There are generally four (4) main types of automotive drive line systems. More specifically, there exists a full-time front wheel drive system, a full-time rear wheel drive system, a part-time four wheel drive system, and an all-wheel drive system. Most commonly, the systems are distinguished by the delivery of power to different combinations of drive wheels, i.e., front drive wheels, rear drive wheels or some combination thereof. In addition to delivering power to a particular combination of drive wheels, most drive systems permit the respectively driven wheels to rotate at different speeds. For example, the outside wheels must rotate faster than the inside drive wheels, and the front drive wheels must normally rotate faster than the rear wheels.
Drive line systems also include one or more Cardan (Universal) and Constant Velocity joints (CVJ's). Cardan joints are the most basic and common joint type used, for example, on propshafts. Although highly durable, Cardan joints are typically not suited for applications with high angles (e.g. >2 degrees) because of their inability to accommodate constant velocity rotary motion. Constant Velocity joints, in contrast, are well known in the art and are employed where transmission of a constant velocity rotary motion is desired or required. For example, a tripod joint is characterized by a bell-shaped outer race (housing) disposed around an inner spider joint which travels in channels formed in the outer race. The spider-shaped cross section of the inner joint is descriptive of the three equispaced arms extending therefrom which travel in the tracks of the outer joint. Part spherical rollers are featured on each arm.
One type of constant velocity universal joint is the plunging tripod type, characterized by the performance of end motion in the joint. Plunging tripod joints are currently the most widely used inboard (transmission side) joint in front wheel drive vehicles, and particularly in the propeller shafts found in rear wheel drive, all-wheel drive and 4-wheel drive vehicles. A common feature of tripod universal joints is their plunging or end motion character. Plunging tripod universal joints allow the interconnection shafts to change length during operation without the use of splines which provoke significant reaction forces thereby resulting in a source of vibration and noise.
Another common type of constant velocity universal joint is the plunging VL or “cross groove” type, which consists of an outer and inner race drivably connected through balls located in circumferentially spaced straight or helical grooves alternately inclined relative to a rotational axis. The balls are positioned in a constant velocity plane by an intersecting groove relationship and maintained in this plane by a cage located between the two races. The joint permits axial movement since the cage is not positionably engaged to either race. As those skilled in the art will recognize, the principal advantage of this type of joint is its ability to transmit constant velocity and simultaneously accommodate axial motion. Plunging VL constant velocity universal joints are currently used for high speed applications such as, for example, the propeller shafts found in rear wheel drive, all-wheel drive and 4-wheel drive vehicles.
The high speed fixed joint (HSFJ) is another type of constant velocity joint well known in the art and used where transmission of high speed is required. High speed fixed joints allow articulation to an angle (no plunge) but can accommodate much higher angles than with a Cardan joint or other non-CV joints such as, for example, rubber couplings. There are generally three types of high speed fixed joints: (1) disk style that bolts to flanges; (2) monoblock style that is affixed to the tube as a center joint in multi-piece propshafts; and (3) plug-on monoblock that interfaces directly to the axle or T-case replacing the flange and bolts.
In a disc-style constant velocity fixed joint, the outer joint member is open on both ends and the cage is assembled from the end opposite the end towards which the cage is urged by the ball expulsion forces under articulated load conditions. Assembly of the cage into the outer joint member is typically accomplished by either incorporating cage assembly notches into one of or a pair of lands in the outer joint member, or by sufficiently increasing the bore diameter of the outer joint part to allow the ball cage to be introduced into the outer joint part.
In a mono-block constant velocity fixed joint, also called a “mono-block high speed fixed joint”, the outer joint part is a bell-shaped member having a closed end. Accordingly, the cage must be assembled from the open end of the outer joint member. To accommodate assembly of the cage into the outer joint part, the bore diameter of the outer joint part must be sufficiently increased to allow assembly and/or assembly notches must be incorporated into at least one opposing pair of the outer joint member lands to allow introduction of the cage.
Driveline systems also commonly include one or more ball spline joints which include a plurality of balls enclosed within a cage to permit rotation around inner and outer respective races. Like constant velocity joints, ball spline joints are adapted to accommodate plunge in the axial direction, i.e. end wise movement. However, unlike constant velocity joints, ball spline joints do not permit articulation at an angle.
A typical driveline system incorporates one or more of the above joints in an all wheel drive or traditional four wheel drive system. In an all wheel drive system, such joints are used to connect a pair of propeller shafts (front and rear)(also called a propeller shaft assembly) to a power take off unit and a rear driveline module, respectively. These propeller shafts (“propshafts”) function to transfer torque to the rear axle in rear wheel and all wheel drive vehicles. Similarly, in a traditional four wheel drive system, such joints are used to connect the propeller shaft between a transfer case and the front axle.
In certain applications, such as, for example, traditional four wheel drive systems, it is desirable to utilize a constant velocity joint/ball spline joint assembly. Many of these prior art applications have had problems in providing a sealing solution for these joint assemblies. Therefore, there is a need in the art to provide a sealing solution which accommodates both articulating and plunging convolutes and which further includes stabilizing features for high speed operation.